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course Phy 121
re-submit
A child in a slowly moving car tosses a ball upward. It rises to a point below the roof of the car and falls back down, at which point the child catches it. During this time the car neither speeds up nor slows down, and does not change direction.
• What force(s) act on the ball between the instant of its release and the instant at which it is caught? You can ignore air resistance.
answer/question/discussion:
Gravity.
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• What happens to the speed of the ball between release and catch? Describe in some detail; a graph of speed vs. clock time would also be appropriate.
answer/question/discussion:
As soon as the ball is released, it will be moving at its fastest velocity. It will begin to slow down until it reaches a point when it stops. At this point, it will begin to fall back to Earth. Initially, it will be moving slowly. The closer it comes to Earth, the faster it will be moving. This will continue until the moment it is caught. If we were to graph this, the x axis would be time and y axis would be velocity or acceleration. The line would appear to be an upside-down bell curve.
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• Describe the path of the ball as it would be observed by someone standing along the side of the road.
answer/question/discussion:
The ball would appear to go up and behind the child. It would appear as an arc.
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• How would the path differ if the child was coasting along on a bicycle? What if the kid didn't bother to catch the ball? (You know nothing about what happens after the ball makes contact with the ground, so there's no point in addressing anything that might happen after that point).
answer/question/discussion:
If the child was coasting along on a bicycle, the ball would go up and come down. The child would continue to move forward.
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• What if the child drops the ball from the (inside) roof of the car to the floor? For the interval between roof and floor, how will the speed of the ball change? What will be the acceleration of the ball? (You know nothing about what happens after the ball makes contact with the floor, so there's no point in addressing anything that might happen after that point).
answer/question/discussion:
The ball would move straight to the back of the car. The ball would reach a point where the velocity would stop and acceleration would be overcoming gravity.
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• What if the child holds the ball out of an open window and drops it. If the ball is dense (e.g., a steel ball) and the car isn't moving very fast, air resistance will have little effect. Describe the motion of the ball as seen by the child. Describe the motion of the ball as seen by an observer by the side of the road. (You know nothing about what happens after the ball makes contact with the ground, so there's no point in addressing anything that might happen after that point).
answer/question/discussion:
The ball would fall to the ground. To the child, it would appear that the ball is moving backwards. As the car is moving forward and the ball is falling to the ground, the motion would appear to move as diagonal.
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Be sure to check the discussion at the link.
Note that you should use the form for the individual 'seed' question, in order to be sure you're provided with the correct link. If you haven't correctly identified the problem, the link will be wrong. However I expect you've identified it accurately, so the link should work.
&#See any notes I might have inserted into your document, and before looking at the link below see if you can modify your solutions. If there are no notes, this does not mean that your solution is completely correct.
Then please compare your old and new solutions with the expanded discussion at the link
Solution
Self-critique your solutions, if this is necessary, according to the usual criteria. Insert any revisions, questions, etc. into a copy of this posted document. Mark any insertions with &&&& so they can be easily identified.If your solution is completely consistent with the given solution, you need do nothing further with this problem. &#
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